Fluidized bed reactor for preventing the fine iron ore from sticking therein and method thereof

ABSTRACT

A smelting reduction apparatus which separates exhaust gas, which is exhausted from a melter-gasifier or a fluidized bed reactor, into dusts and reducing gas to supply them to each fluidized bed reactor respectively is disclosed, in which the smelting reduction apparatus includes a three-stage type fluidized bed reactor, a melter-gasifier for manufacturing molten pig iron by finally reducing the fine iron ores of which reaction is finished in a final fluidized bed reactor, and a dust separating device, which performs separation of exhausted gas from the melter-gasifier into dusts and reducing gas, so as to supply the separated reducing gas to a lower part of the final fluidized bed reactor, dusts having a larger particle sizes in the separated dusts to the melter-gasifier again, and fine dusts having a smaller particle sizes in the separated dusts to an upper part of a gas distributor of the final fluidized bed reactor.

BACKGROUND OF THE INVENTION

[0001] a) Field of the Invention

[0002] The present invention relates to smelting reduction process and,more particularly, to a smelting reduction apparatus which separatesexhaust gas, which is exhausted from a melter-gasifier or a fluidizedbed reactor, into dusts and reducing gas to supply them to acorresponding fluidized bed reactor respectively.

[0003] (b) Description of the Related Art

[0004] Generally, a blast furnace has been extensively used to make ironthrough reducing and melting iron ores. However, the blast furnaceinvolves a drawback that the charging materials should be pre-treated tobear is agglomerated forms such as sintered iron ores and cokes.

[0005] In order to solve such a problem, a smelting and reductionprocess has been developed for the direct use of fine iron ores and coalwithout pretreatment.

[0006] The smelting reduction process is composed of a preliminaryreduction process and a final reduction process. In the preliminaryreduction process, the charged fine iron ores are pre-heated and thenpreliminarily reduced. In the final reduction process, a sponge ironwhich is reduced in the preliminary reduction process is finally reducedand melted in the presence of high pressure oxygen and coal to therebyform a molten iron.

[0007] The fluidized bed reduction reactor (hereinafter, referred to“fluidized bed reactor”) is used as an equipment for the preliminaryreduction process, and a melter-gasifier is used as an equipment for thefinal reduction process.

[0008] The preliminary reduction process is typically divided into amoving bed type and a fluidized bed type according to a contact statebetween raw iron ores and reducing gas. It is efficient to apply thefluidized bed type preliminary reduction process rather than the movingbed type if the charged iron ore has a small particle size and a wideparticle size distribution.

[0009] Korean Patent No. 117065 discloses an apparatus for such afluidized bed type preliminary reduction process. According to thispatent, a device for uniformly reducing a fine iron ore having a wideparticle size distribution in a fluidized bed reactor is proposed. Inorder to achieve such a uniform reducing of the fine iron ore, thepatent provides a three-stage type fluidized reactor which is designedin a conical shape having a wide upper part and a narrow lower part,wherein the iron ore is reduced through three stages of pre-heating,pre-reducing and final preliminary reducing. This patent also proposes acyclone for collecting fine iron ore, which is discharged, from an upperpart of the respective fluidized bed reactors by scattering to supply toa bottom part of the respective fluidized bed reactors.

[0010] According to this patent designed as above, the fine iron orehaving the wide particle size distribution may be efficiently reducedwhile maintaining stable fluidized state.

[0011] This patent has, however, a disadvantage that a gas distributorof the fluidized bed reactors may be clogged by dusts dust contained inthe reducing gas. That is, a large amount of dusts is included inexhaust gas, which is discharged from the melter-gasifier and suppliedto the fluidized bed reactors. If the dusts are supplied to the gasdistributor of a final reduction furnace, the dust becomes stuck tonozzles, which are mounted in the gas distributor, and if the stickingphenomenon is accumulated, the gas distributor itself becomes clogged.

[0012] If the gas distributor is clogged as above, it becomes impossibleto maintain a uniform flow of the reducing gas in the fluidized bedreactors, and more severely, operations should be stopped.

SUMMARY OF THE INVENTION

[0013] Therefore, the present invention is derived to resolve the abovedisadvantages and problems of the related art and has an object toprovide a smelting and reduction apparatus which can separate exhaustgas, which is exhausted from a melter-gasifier or a fluidized bedreactor, into dusts and reducing gas to supply them to each fluidizedbed reactor respectively.

[0014] It is another object of the present invention to provide a methodfor manufacturing molten pig iron by a smelting and reduction process,which can prevent sticking of particles of fine iron ores and cloggingof a gas distributor by coating separated dusts on a surface of theparticles of the fine iron ores which is flowing in the fluidized bedreactors.

[0015] This and other objects may be achieved by the present invention,which is described in detail hereinafter.

[0016] According to one aspect of the present invention, a smelting andreduction apparatus includes a three-stage type fluidized reactor, amelter-gasifier for manufacturing molten pig iron by finally reducingfine iron ores of which reaction is finished in a final fluidizedreactor, and a dust separating device, which performs separation ofexhausted gas from the melter-gasifier into dusts and reducing gas so asto supply the separated reducing gas to a lower part of the finalfluidized bed reactor, dusts having a larger particle sizes in theseparated dusts to the melter-gasifier again, and fine dusts having asmaller particle sizes in the separated dusts to an upper part of a gasdistributor of the final fluidized bed reactor.

[0017] The three-stage type fluidized bed reactor of the presentinvention includes a) an or e charging duct mounted on a side ofrespective fluidized bed reactors for charging fine iron ores, b) a gassupply duct mounted at a lower part of the respective fluidized bedreactors, c) an ore discharge duct mounted on a side wall of therespective fluidized bed reactors for discharging fine iron ores whichare charged into the respective fluidized bed reactors and reactionsthereof are finished, d) a gas distributor mounted in the respectivefluidized bed reactors for uniformly dispersing reducing gas into therespective fluidized bed reactors, and e) a cyclone for separating fineiron ore particles from the reducing gas, which is discharged from theupper parts of the respective fluidized bed reactors, to supply thereducing gas to next reactor or discharge outside and recycle the fineiron ore particles to the lower parts of the respective fluidized bedreactors.

[0018] In the present invention, each fludized bed reactor ismanufactured in a dual-stage cylindrical shape of which a diameter of alower part is small and a diameter of an upper part is large so thatlower and the upper parts are to connected to each other slantingly. Inthe dual-stage cylindrical fluidized bed reactors, the diameter of theupper cylindrical part is larger than that of the lower cylindrical partby 1.5˜2.0 times, and the inclination of the connection between theupper and lower cylindrical parts is 20˜30° with relation to a centralaxis of the fluidized bed reactors. A whole height of the fluidized bedreactors is larger than a diameter of the lower cylindrical part by10˜20 times.

[0019] In the present invention, the dust separation device is formed ofat least two or more cyclones and at least one or more dust storagebins. A first cyclone of the cyclones is connected to the upper part andthe lower part of the melter-gasifier and an upper part of a secondcyclone. The second cyclone is connected to the lower part of the finalfluidized bed reactor and an upper part of the dust storage bin and thedust storage bin is connected to an upper part of the gas distributor ofthe final fluidized bed reactor.

[0020] In the dust separation device, the second cyclone and the duststorage bin is connected by a dust supply duct which is mounted with atwo-way valve, wherein the dust supply duct branched by the two-wayvalve is connected to a dust supply duct which connects the firstcyclone and the melter-gasifier.

[0021] The dust storage bin part is formed of three dust storage binsrespectively connected to one another via the dust supply ducts. Thedust supply duct which is positioned at a lower part of a first duststorage bin is mounted with a nitrogen gas injection device, so thatdusts stored in the first dust storage bin can be pneumaticallytransported to a second dust storage bin with high pressure nitrogengas. A dust supply duct which is positioned at a lower part of a thirddust storage bin is also mounted with a nitrogen gas injection device,so that the dusts stored in the third dust storage bin can be introducedinto the final reactor with high pressure nitrogen gas.

[0022] On the other hand, a dust supply duct connecting the lower partof the third dust storage bin to the nitrogen gas injection device ismounted with a dust introducing feeder for controlling the amount ofdust supply to the final reactor. Further, each of the dust supply ductsis mounted with a control valve for controlling a supply of the dustsconveyed to the dust supply ducts.

[0023] The molten pig iron is manufactured from the fine iron ores byusing the smelting reduction apparatus hereinabove.

[0024] The process for manufacturing the molten pig iron by using thesmelting reduction apparatus of the present invention is characterizedin that the exhaust is gas discharged from the melter-gasifier isseparated into reducing gas and dusts to be supplied to the finalfluidized bed reactor.

[0025] Even though the separated reducing gas is directly supplied tothe lower part of the final fluidized bed reactor, the dusts areseparated again such that the fine dusts having a smaller particle sizeis blown into the upper part of the gas distributor of the finalfluidized bed reactor by high pressure nitrogen.

[0026] As the fine dusts are blown into the fluidized bed reactor, thefine dusts are coated on surfaces of the fine iron ores, so that thesticking between the fine iron ores and the gas distributor may beprevented.

[0027] The pressure of the nitrogen for the injection of dust particlesis controlled higher than an internal pressure of the final fluidizingbed reactor by 2˜3 times.

[0028] A velocity of the reducing gas in the respective fluidizing bedreactors is preferably controlled 1.2˜1.5 times of a minimum fluidizingvelocity of the fine iron ores residing in the fluidizing bed reactors.

[0029] If the molten pig iron is manufactured by the process describedhereinabove, the sticking between the fine iron ores and the gasdistributor may be prevented, thereby effectively preventing operationobstacles of the smelting reduction process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] A more complete appreciation of the invention, and many of theattendant advantages thereof, will be readily apparent as the samebecomes better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawing, in which like reference symbols indicate the same or thesimilar components, wherein:

[0031]FIG. 1 is a structural view of a smelting reduction apparatusincluding a three-stage type fluidized bed reactor according to apreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Preferred embodiments of this invention will be explained withreference to the accompanying drawing.

[0033]FIG. 1 illustrates a structural view of a smelting reductionapparatus including three-stage type fluidized bed reactors.

[0034] As shown in FIG. 1, the smelting reduction apparatus includes athree-stage type fluidized bed reactor and a melter-gasifier 40.

[0035] The three-stage type fluidized bed reactors include a pre-heatingfurnace 10, a pre-reducing furnace 20, and a final reducing furnace 30.

[0036] The pre-heating furnace 10 is mounted with an ore charging duct 1on a side wall for charging fine iron ores which fall down from acharging bin 5, a gas supply duct 28 at a lower part for supplyingreducing gas which is discharged from the pre-reducing furnace 20, and afirst cyclone 15 at an upper part. The first cyclone 15 collects fineparticles of ores which are included in the exhaust gas discharged via agas discharging duct 13 and re-supplies the fine ore particles to thelower part of the pre-heating furnace 10. The exhaust gas from which thefine ore particles are removed is released outside via a discharge duct16, which is mounted at an upper part of the cyclone 15.

[0037] The pre-reducing furnace 20 is mounted with an ore dischargingduct 11 on a side wall for supplying the fine iron ores which arepreheated in the pre-heating furnace 10, a gas supply duct 38 at a lowerpart for supply reducing gas which is discharged from the final reducingfurnace 30, and a second cyclone 25 at an upper part. The second cyclone25 collects fine particles of ores which are included in the exhaust gasdischarged via a gas discharging duct 23 and re-supplies the fine oreparticles to a lower part of the pre-reducing furnace 20. The exhaustgas from which the fine ore particles are removed is supplied to thelower part of the pre-heating furnace 10 via a gas supply duct 28 whichis mounted at an upper part of the cyclone 25.

[0038] The final reducing furnace 30 is mounted with an ore dischargingduct 21 on a side wall for supplying the fine iron ores which arepre-reduced in the pre-reducing furnace 20, a gas supply duct 58 at alower part for supply reducing gas which is discharged from themelter-gasifier 40, and a third cyclone 35 at an upper part. The thirdcyclone 35 collects fine particles of ores which are included in theexhaust gas discharged via a gas discharging duct 33 and re-supplies thefine ore particles to a lower part of the final reducing furnace 30. Theexhaust gas from which the fine ore particles are removed is supplied tothe lower part of the pre-reducing furnace 20 via a gas supply duct 38which is mounted at an upper part of the cyclone 35.

[0039] As for the shape of the respective fluidized bed reactors asdescribed above, the pre-heating furnace 10, the pre-reducing reactor 20and the final reducing reactor 30 has a small diameter in the lowerparts 10 a, 20 a, and 30 a, a large diameter in the upper parts 10 b, 20b, and 30 b, and the slantingly formed cylindrical connection parts 10c, 20 c, and 30 c. Therefore, the whole shape of the respectivefluidized bed reactors is formed in the dual-stage cylinder having thenarrow lower parts and the wide upper parts.

[0040] The diameter of the upper parts 10 b, 20 b and 30 b of therespective fluidized bed reactors is formed in the range of 1.5˜2.0times of the diameter of the lower parts 10 a, 20 a and 30 a, such thatthe velocity of the gas in the upper parts of the respective fluidizedbed reactors is decreased for preventing the fine iron ores from beingdischarged as they are.

[0041] The whole height of the respective fluidized bed reactors ispreferably formed 10˜20 times of the diameter of the lower parts 10 a,20 a and 30 a. If the respective fluidized bed reactors are formed inthe elongated dual-stage cylindrical shape, a space in which the fineiron ores flow is sufficiently assured and the fine iron ores areprevented from being discharged as they are. Further, height of thecylindrical lower parts 10 a, 20 a and 30 a is preferably formed in1.0˜1.5 times of height of the cylindrical upper parts 10 b, 20 b and 30b, and the inclination of the connecting parts 10 c, 20 c and 30 c ispreferably formed inclined by 20˜30° with relation to the central axesof the respective fluidized bed reactors.

[0042] The fine iron ores which are preliminary reduced in the finalreducing furnace 30 of the three-stage type fluidized bed reactors asabove, are supplied to the upper part of the melter-gasifier 40 whichwill be described hereinafter via an ore discharging duct 31. Theexhaust gas, which is discharged from the melter-gasifier 40, is,however, not directly supplied to the final reducing furnace 30 but viathe dust separation device, which will be described hereinafter.

[0043] The dust separation device according to the present invention ismounted between the melter-gasifier 40 and the final reducing furnace 30and includes two cyclones and three dust storage bins which are disposedin series.

[0044] Now, the dust separation device will be described in more detail.

[0045] First, a fourth cyclone 45, which is a first element of the dustseparation device, is connected to the melter-gasifier 40, through anexhaust gas discharging duct 43 and a first dust supply duct 46. Thefourth cyclone 45 is supplied with high temperature exhaust gas from themelter-gasifier 40 via the exhaust gas discharging duct 43 and primarilyseparate dusts which are included in the exhaust gas to collect. Thedusts collected by the fourth cyclone 45 are supplied to themelter-gasifier 40 via the first dust supply duct 46. Reducing gas fromwhich the dusts are primarily removed in the fourth cyclone 45 issupplied to a fifth cyclone 50 which will be described hereinafter viaan exhaust gas discharging duct 47 which is mounted at an upper part ofthe fourth cyclone 45.

[0046] The fifth cyclone 50 separates and collects dusts of an ultrafine particle shape which are included in the reducing gas which issupplied from the fourth cyclone 45 but not separated by the fourthcyclone 45. The ultra fine dusts collected by the fifth cyclone 50 aresupplied to a first dust storage bin 60 via a second dust supply duct 51which is connected to a lower part of the fifth cyclone 50, wherein thesecond dust supply duct 51 is mounted with a two-way valve 52 so thatthe dusts collected in the fifth cyclone 50 are partially re-supplied tothe melter-gasifier 40 via a third dust supply duct 57 as necessary. Thethird dust supply duct 57 may be directly connected to themelter-gasifier 40 and is more preferably connected to the first dustsupply duct 46.

[0047] The fifth cyclone 50 is connected to a reducing gas dischargeduct 58 at an upper part to supply the reducing gas from which the dustsare removed to the final reducing furnace 30.

[0048] The first dust storage bin 60 is mounted with a first nitrogeninjection device N1 at a lower part for conveying the stored ultra finedusts to a second dust storage bin 70. The first dust storage bin 60 isconnected to the dust storage bin 70 via a dust conveying duct 61.

[0049] The second dust storage bin 70 is connected to a third duststorage bin 80 via a fourth dust supply duct 71, so that the ultra finedusts collected in the second dust storage bin 70 are supplied to thethird dust storage bin 80 via the fourth dust supply duct 71.

[0050] A lower part of the third dust storage bin 80 is connected to anupper part of a gas distributor 32 of the final reducing furnace 30 viaa fifth dust supply duct 81. The fifth dust supply duct 81 is mountedwith a dust charging feeder 82 at an upper part for controlling theamount of dusts which are supplied to the final reducing furnace 30. Thedust charging feeder 82 is mounted with a second nitrogen-injectiondevice N2 at a lower part for introducing the ultra fine dusts to thefinal reducing furnace 30 with high pressure. Accordingly, the ultrafine dusts which are injected into the upper part of the gas distributor32 of the final reducing furnace 30 with the high pressure by the secondnitrogen-injection device N2 are coated on surfaces of the fine ironores in the final reducing furnace 30.

[0051] The dust separation device of the present invention as describedabove, is mounted with control valves 53, 63, 73, and 83 on therespective dust supply ducts for stopping the flow of the dusts and gasin case of operating or repairing the device if it is necessary.

[0052] Now the method for manufacturing the molten pig iron by meltingthe fine iron ores of a wide particle size distribution by using thesmelting reduction apparatus of the present invention will be describedin more detail.

[0053] First, the fine iron ores fallen down from a charging bin 5 aresupplied to a side of the pre-heating furnace 10 via an ore chargingduct 1, the iron ores of fine particles which are collected in the firstcyclone 15 are supplied to a side of the pre-heating furnace 10 via afirst circulation duct 17, and the high temperature reducing gas whichis discharged from the pre-reducing furnace 20 is supplied to a lowerpart of the pre-heating furnace 10 via the gas supply duct 28. The fineiron ores and the iron ores of fine particles, which are supplied to thepre-heating furnace 10, are preheated by the reducing gas in thepre-heating furnace 10, forming a bubbling fluidized bed.

[0054] The pre-reducing furnace 20 is supplied with the fine iron orespreheated by the pre-heating furnace 10 via an ore charging duct 11 to aside, as well as the iron ores of fine particles, which are collected inthe second cyclone 25, via a second circulation duct 27 to a side.Further the pre-reducing furnace 20 is supplied with the hightemperature reducing gas discharged from the final reducing furnace 30to its lower part via a gas supply duct 38. The fine iron ores and theiron ores of fine particles, which are supplied to the pre-reducingfurnace 20, are pre-reduced by the reducing gas in the pre-reducingfurnace 20, forming a bubbling fluidized bed.

[0055] The final reducing furnace 30 is supplied with the fine iron orespre-reduced by the pre-reducing furnace 20 via an ore charging duct 21to a side, as well as the iron ores of fine particles, which arecollected in the third cyclone 35, via a third circulation duct 37 to aside. Further the final reducing furnace 30 is supplied with the hightemperature reducing gas discharged from the fourth cyclone 50 to itslower part via a gas supply duct 58. The fine iron ores and the ironores of fine particles which are supplied to the final reducing furnace30 are finally preliminary reduced by the reducing gas in the finalreducing furnace 30, forming a bubbling fluidized bed.

[0056] As above, fine particle sponge iron, which is sequentiallypreliminary reduced while passing through the three-stage type fluidizedbed reactor, are charged into the upper part of the melter-gasifier 40via the ore discharge duct 31. The melter-gasifier 40 is supplied withcoal and high pressure oxygen in addition to the sponge iron which issupplied from the final reducing reactor 40 so as to finally reduce thesponge iron and melt, thereby producing the molten pig iron.

[0057] The melter-gasifier 40 generates a lot of exhaust gas of hightemperature in the process of melting the sponge iron.

[0058] The exhaust gas contains ultra fine dusts which contains a lot ofcarbon and carbonized gas generated in the process of the burning of thecharged coal. The dusts contained carbon and carbonized gas aresequentially separated by the dust separation device of the presentinvention. Now, the process for separating the exhaust gas will bedescribed in more detail.

[0059] The exhaust gas, which is discharged from the melter-gasifier 40,is supplied to the fourth cyclone 45 via the discharge duct 43. Theexhaust gas supplied to the cyclone is separated into dusts in theparticle state and carbonized gas in the gas state by a strongcentrifugal force, wherein the separated dusts are fallen down to alower part in the cyclone and the carbonized gas is gathered to an upperpart in the cyclone. The separated dusts collected to the lower part arere-supplied to the melter-gasifier 40 via the first dust supply duct 46,while the separated carbonized gas is discharged to the fifth cyclone50, containing the ultra fine dusts which are not separated.

[0060] The fifth cyclone 50 secondarily collects the ultra fine dustsincluded in the supplied carbonized gas The carbonized gas from whichthe ultra fine dusts are separated is supplied to the final reducingfurnace 30 to be used as the reducing gas. The ultra fine dustscollected in fifth cyclone 50 are supplied to the melter-gasifier 40 orthe first dust storage bin 60.

[0061] The dusts discharged to the first dust storage bin 60 areconveyed to the second dust storage bin 70 by the first nitrogeninjection device N1 and continuously supplied to the third dust storagebin 80.

[0062] The dusts stored in the third dust storage bin 80 are injected tothe upper part of the gas distributor 32 of the final reducing furnace30 by the second is nitrogen injection device N2 and coat the fine ironore particles which are in bubbling fluidization state in the finalreducing furnace 30.

[0063] At this time, the pressure of the nitrogen supplied by the firstand second nitrogen injection devices N1 and N2 is higher than thepressure in the furnace by 2˜3 times. The dusts are smoothly conveyedand stabled injected in the final reducing furnace 30 by the highpressure of the nitrogen.

[0064] An amount of the dusts which are introduced into the finalreducing furnace 30 is preferably controlled to be 0.5˜1.0 wt % withrelation to an amount of raw iron ores which are charged into thepre-heating furnace 10. If the amount of the dusts which are introducedinto the final reducing furnace 30 is less than 0.5 wt %, stickingprevention effect between the fine iron ores becomes reduced, while ifthe amount exceeds 1.0 wt %, the gas distributor may be clogged by theultra fine dusts in next process.

[0065] It is preferable to control a velocity of the reducing gas in thepre-heating furnace 10, the pre-reducing furnace 20 and the finalreducing furnace 30 in the range of 1.2˜1.5 time of a minimum fluidizingvelocity of the fine iron ores which are staying in the furnaces. Bymaintaining the velocity of the reducing gas as above, the respectivefluidized bed reactors may form a stable bubbling fluidized bed.

[0066] Now, preferred embodiments are suggested to help the apparentunderstanding of the present invention. The below embodiments areprovided for the sake of clear understanding only and the presentinvention is not limited thereto.

Embodiment

[0067] The specification and experimental conditions for the smeltingreduction apparatus of the preferred embodiment of the present inventionis as follows.

[0068] 1) Specification of the fluidized bed reactor (the pre-heatingfurnace, the pre-reducing furnace, and the final reducing furnace)

[0069] Radius of the lower cylindrical part: 0.3 m

[0070] Radius of the upper cylindrical part: 0.6 m

[0071] Height of the lower cylindrical part from the upper part of thegas distributor: 3 m

[0072] Height of the upper cylindrical part from lower part of theinclination part: 3 m

[0073] 2) Fine iron ores

[0074] Particle size of the fine iron ores: under 10 mm

[0075] Particle size distribution of the fine iron ores:

[0076] under 0.125 mm: 15.5%, 0.1250 0.25 mm: 10.0%,

[0077] 0.25 0.5 mm: 9.1%, 0.51 0.0 mm 9.2%,

[0078] 1.0 3.0 mm: 22.2% 3.05.8 0.0 mm: 19.5%

[0079] 5.0 8.0 mm:13.7% 8.01 0.0 mm: 0.8%

[0080] Chemical composition of the fine iron ores

[0081] T. Fe: 63.49 wt %, FeO: 0.37 wt %, SiO₂: 4.32 wt %,

[0082] Al₂O₃: 2.33 wt %, Mn: 0.05 wt %, S :0.007 wt %,

[0083] P: 0.063%, crystal water: 5.41 wt %

[0084] 3) Reducing gas

[0085] Composition: CO: 65%, H₂: 25%, CO₂: 5%, N₂: 5%

[0086] Temperature: 750-850

[0087] Pressure: 2.0-3.0 barg

[0088] 4) Chemical composition of the dusts

[0089] T. Fe: 25-33 wt %, FeO: 10-15 wt %, SiO₂: 8-10 wt %,

[0090] M. Fe: 10-15 wt %, Al₂O₃: 2-5 wt %, CaO: 2-5 wt %,

[0091] MgO: 1-2%, C: 45-55 wt %, S: 1-5 wt %,

[0092] Several experiments were carried out with the smelting reductionapparatus to examine the reduction of the fine iron ores.

[0093] The experimental results exhibited that reduced fine iron oreswas begun to be discharged via the ore discharging duct 31 from thefinal reducing furnace 30 after 90 minutes from the beginning of thecharging of the fine iron ores from the charging bin 5 into thepre-heating furnace 10.

[0094] An average reduction degree of the fine iron ores which aredischarged from the final reducing furnace 30 was exhibited 86˜90%, veryexcellent. An average gas utilization degree was 30˜35%, and the gasconsumption rate was 1350-1500 Nm³/t-ore. Further, a difference ofpressure between the upper part and the lower part of the gasdistributor of the final reducing furnace 30 was maintained in the rangeof 20-30 mbar, which was not increased even after a long time. As above,the small difference of pressure between the upper and lower parts ofthe gas distributor means that the clogging phenomenon of the gasdistributor nozzle did not occur. Finally, the particle sizedistribution of the reduced iron which is preliminary reduced anddischarged finally was exhibited uniform, which means that the stickingphenomenon between the fine iron ores did not occur in the respectivefluidized bed reactors.

[0095] As shown from the result of the above embodiment, the smeltingreduction apparatus according to the present invention may effectivelyprevent the clogging phenomenon of the gas distributor nozzle due to thedusts which is apt to occur in the related art fludized bed reactors.

[0096] Further, the sticking phenomenon between the reduced ironparticles which may occur in the process of the reduction of the fineiron ores may be prevented by supplying the dusts containing a lot ofcarbon into the fluidizing bed reactors to coat the surfaces of thereduced iron.

[0097] While the present invention has been described in detail withreference to the preferred embodiment, those skilled in the art willappreciate that various modifications and substitutions can be madethereto without departing from the spirit and scope of the presentinvention as set forth in the appended claims.

What is claimed is:
 1. A smelting reduction apparatus for preventingsticking of charged fine iron ores in fluidized bed reactors,comprising: a three-stage type fluidized bed reactors including; a) anore charging duct mounted on a side of respective fluidized bed reactorsfor charging fine iron ores, b) a gas supply duct mounted at a lowerpart of the respective fluidized bed reactors for supplying reducinggas, c) an ore discharge duct mounted on a side wall of the respectivefluidized bed reactors for discharging fine iron ores which are chargedinto the respective fluidized bed reactors and reactions thereof arefinished, d) a gas distributor mounted in the respective fluidized bedreactors for uniformly distributing the reducing gas to the inner spaceof the respective fluidized bed reactors, and e) a cyclone forseparating fine iron ore particles from the exhausted gas, which isdischarged from the upper parts of the respective fluidized bedreactors, to supply the reducing gas to next reactor or release outsideand recycle the fine iron ore particles to the lower parts of therespective fluidized bed reactors; a melter-gasifier for manufacturingmolten pig iron by finally reducing the fine iron ores of which reactionis finished in a final fluidized reactor, and a dust separating device,which performs separation of exhausted gas from the melter-gasifier intodusts and reducing gas, so as to supply the separated reducing gas to alower part of the final fluidized bed reactor, dusts having a largerparticle sizes in the separated dusts to the melter-gasifier again, andfine dusts having a smaller particle sizes in the separated dusts to anupper part of a gas distributor of the final fluidized bed reactor.
 2. Asmelting reduction apparatus of claim 1, wherein each of the fluidizedbed reactors of the three-stage type fluidized bed reactor ismanufactured in a dual-stage cylindrical shape, in which a diameter of alower part is small and a diameter of an upper part is large so thatlower and the upper parts are connected to each other slantingly.
 3. Asmelting reduction apparatus of claim 2, wherein the diameter of theupper cylindrical part is larger than that of the lower cylindrical partby 1.5˜2.0 times.
 4. A smelting reduction apparatus of claim 3, whereina height of the cylindrical lower parts is higher by 1.0˜1.5 times thanthat of the cylindrical upper parts,
 5. A smelting reduction apparatusof claim 4, wherein the inclination of the connection between the upperand lower cylindrical parts is 20˜30° with relation to a central axis ofthe fluidized bed reactors.
 6. A smelting reduction apparatus of claim5, wherein a whole height of the fluidized bed reactors is larger than adiameter of the lower cylindrical part by 10˜20 times.
 7. A smeltingreduction apparatus of claim 1 or claim 2, wherein the dust separationdevice includes at least two or more cyclones and at least one or moredust storage bins, wherein a first cyclone of the cyclones is connectedto the upper part and the lower part of the melter-gasifier and an upperpart of a second cyclone, the second cyclone is connected to the lowerpart of the final fluidized bed reactor and an upper part of the duststorage bin, and the dust storage bin is connected to an upper part ofthe gas distributor of the final fluidized bed reactor.
 8. A smeltingreduction apparatus of claim 7, wherein the second cyclone and the duststorage bin is connected by a dust supply duct which is mounted with atwo-way valve, wherein the dust supply duct branched by the two-wayvalve is connected to a dust supply duct which connects the firstcyclone and the melter-gasifier.
 9. A smelting reduction apparatus ofclaim 8, wherein the dust storage bin part includes three dust storagebins respectively connected to one another via the dust supply ducts.10. A smelting reduction apparatus of claim 9, wherein a dust supplyduct which is positioned at a lower part of a first dust storage bin ismounted with a nitrogen gas injection device, so that dusts stored inthe first dust storage bin may be conveyed to a second dust storage binwith high pressure.
 11. A smelting reduction apparatus of claim 10,wherein a dust supply duct which is positioned at a lower part of athird dust storage bin is mounted with a nitrogen gas injection device,so that the dusts stored in the third dust storage bin may be injectedinto the final reactor with high pressure.
 12. A smelting reductionapparatus of claim 11, wherein a dust supply duct connecting the lowerpart of the third dust storage bin to the nitrogen gas injection deviceis mounted with a dust introducing feeder for controlling an amount ofdust supply to the final reactor.
 13. In a smelting reduction process inwhich fine iron ores are charged into a three-stage type fludizing bedreactor and supplied with reducing gas for manufacturing sponge iron byreducing the charged fine iron ores, and molten pig iron is manufacturedby charging the sponge iron into a melter-gasifier, a process formanufacturing molten pig iron by using the smelting reduction processcharacterized in that exhaust gas discharged from the melter-gasifier isseparated into reducing gas and dusts, the separated reducing gas issupplied to a lower part of a final fluidized bed reactor, and finedusts having a smaller particle sizes in the separated dusts aresupplied to an upper part of a gas distributor of the final fluidizedbed reactor for coating fine iron ores which are in bubblingfluidization state in the respective fluidizing bed reactors so as toprevent sticking of the fine iron ores to each other and to the gasdistributor.
 14. A process for manufacturing molten pig iron of claim13, wherein the fine dusts having a smaller particle sizes are suppliedto the final fluidized bed reactor by high pressure nitrogen.
 15. Aprocess for manufacturing molten pig iron of claim 14, wherein thepressure of the nitrogen for conveying the dust particles is higher thanan internal pressure of the final fluidizing bed reactor by 2˜3 times.16. A process for manufacturing molten pig iron of claim 15, wherein anamount of the dusts which are injected into the final reducing furnaceis to be 0.5˜1.0 wt % with relation to an amount of raw iron ores whichare initially charged into the fluidizing bed reactors.
 17. A processfor manufacturing molten pig iron of claim 16, wherein a velocity of thereducing gas in the fluidizing bed reactors is to be 1.2˜1.5 times of aminimum fluidizing velocity of the fine iron ores which are staying inthe fludizing bed reactors.